Harsh Downshift

I recently purchased a 2002 Stratus and as I always do, I got the oil changed and had a transmission "service" performed. But now I notice the transmission downshifts very hard at about 25 MPH, it never did that before. I took it back to the mechanic and he can't figure out why it's doing it. I read somewhere that sometimes after a change in transmission fluid the transmission computer need to "relearn", presumably shift points. Does anyone have any thoughts on whether or not this might work, and how to accomplish it?

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A shop with the proper computer (believe it's drbIII), can do a "quick learn" to fix it. Otherwise, just go with the flow for now and it will eventually learn your driving and it's own optimal shift points. Perfectly normal with the 41te trans

Thanks! It's weird, it downshifts fine the first "cycle" after I start it up, but after that it downshifts very hard at about 25 mph. I tried driving it with o/d off (which I assume is the "3" gear selection option) and it downshifts fine...??? cars..go figure.

Did they use ATF4 when they flushed it? I almost had my car flushed by firestone when I asked them if they would use ATF4. They looked in there computer and said they would fill it with some thing else. I said forget it. I'll do it my self. I ended up dropping the pan at least 4 or five times during the summertime...

The symptoms of using the wrong fluid, be it +3 or some other ATF, is usually a fluttering or slipping during your upshift, not a thump during your downshift.

Either way though, some other ATF plus their special additive can be very bad for these 41te transmissions. If they didn't use ATF+4 demand that they flush it and use the proper stuff, as per the Dodge service manual. At best it can keep the transmission from learning properly (or slip/flutter), worst case, it will kill it. I would see to it that it was done right.

For what its worth Downshifts under hard-ish braking will seem jerky with new fluid becuase it is a slush box auto and not some super car twin disk with rev matching. Essentially the trans decides to change gears and engages the lower gear which will not match the engine speed which will drop to idle in the half second or more it takes for the new gear to be selected. So the car will lurch forwards becuase the wheel speed and "new" gear result in a higher engine speed. So you have a lower gear with more torque multiplication and the engine surging to a higher RPM speed. While braking this change is very pronounce as you brake the trans disengages which mean the engine is no longer trying to move the car so you slow down faster, the trans grabs another gear the motor jumps in speed and as a result the throttle plate opens and more fuel is introduced, so the motor begins to work against the brakes again and the car will "lurch".

As the trans begins to "re-learn" it will change shift points to lessen this. That's why these care are so difficult to tune the PCM is very good at recognizing something out of whack and correcting it.